So, basically you want them to wear some kind of yellow badge?
*Sarcasm* And then, if they steal your mobs or do something to make you mad, you can report them and have their character deleted....
In all seriousness though, F2P will help the game. Ostracizing F2P'ers will just encourage them to quit instead of invest in the economy of the game. Think about it.
P.S.: Though I'm also guilty (as I am posting), but we really shouldn't feed trolls. They are like stray cats. Once you feed them once they come back. When you continue to feed them, they grow in numbers.